1. Field of the Invention
The invention relates to neutralization of aldehydes for the purpose of complying with waste disposal requirements established by federal and state environmental protection agencies, in particular, with forming non-reversible neutralized aldehydes which do not revert back to toxic aldehydes.
2. Description of Related Art
Waste disposal of aldehydes has become increasingly more difficult over the years. Treatment of wastes containing a certain amount of aldehyde prior to placement of the waste into the environment is required by law. The extent of such treatment may vary depending upon the location of where the waste is generated and the stringency of the environmental standards in that area. For example, waste containing aldehyde may be classified as a hazardous waste in California under 22 CAL. CODE REGS., TIT. 22, xc2xa766696. Formaldehyde also may be considered a hazardous waste on the federal level under 40 C.F.R. xc2xa7261.33(e) if it is a commercial chemical product (e.g., pure technical grade formaldehyde or formaldehyde is the sole active ingredient of the product that is to be disposed). Every state has an environmental regulation that is at least as stringent as this formaldehyde standard. State regulations also may be more stringent than this standard.
Additionally, facilities that discharge waste water to Publicly Owned Treatment Works (xe2x80x9cPOTWxe2x80x9d) or directly into navigable waters may be required to meet standards that are established by a government agency. The standard may vary for each facility depending upon the quality of the receiving water and the concentration of aldehyde found in the waste water that is discharged into the environment by industry in that area.
Waste containing aldehyde may be generated by a variety of processes. For example, aldehydes such as glutaraldehyde and ortho-phthalaldehyde (xe2x80x9cOPAxe2x80x9d) are used in disinfecting medical devices or instruments. Waste containing aldehydes also may be generated by painting operations, stripping operations related to floors, or other manufacturing operations.
Typically, ammonia and sodium bisulfite (xe2x80x9cSBSxe2x80x9d) are used to treat many aldehydes. These compounds, however, have not proven to be effective at neutralizing OPA in accordance with environmental regulations.
A waste is classified as a hazardous waste in California if the waste being examined xe2x80x9chas an acute aquatic 96-hour LC50 less than 500 milligrams per liter (mg/L) when measured in soft water (total hardness 40 to 48 milligrams per liter of calcium carbonate) with fathead minnows . . . xe2x80x9d 22 CAL. CODE REGS., TIT. 22, xc2xa766696. LC50 represents the concentration of a waste that is necessary to kill 50% of a particular animal exposed to a waste.
Note that a nonhazardous waste is generally considered by federal and state environmental agencies as a waste that does not satisfy the criteria set forth in defining a hazardous waste. Therefore, wastes generated in California that have a LC50 greater than 500 mg/L are nonhazardous wastes and wastes having LC50 less than 500 mg/L are classified as hazardous. SBS, for example, in combination with OPA, produces a product that is generally considered hazardous under California environmental law as shown in Table 1 by LC50 being consistently below 500 mg/L. For this study, CIDEX(copyright)OPA (commercially available from Advanced Sterilization Products(copyright), a Johnson and Johnson Company of Irvine, Calif.) was used to supply the OPA.
In addition to lacking the ability to effectively neutralize OPA, ammonia and SBS are problematic since they may be harmful to the environment.
FIG. 1 shows that when OPA is combined with SBS at the molar ratio of SBS/OPA=4:0 for 30 minutes, OPA has been neutralized since the OPA concentration is nondetectable in a high performance liquid chromatography (HPLC) analysis method, which has detection limit for OPA at 10 ppm. However, the end product is still classified as a hazardous waste as shown in Table 1. Therefore, even though the aldehyde is neutralized completely by a neutralizer, the end product may still be a hazardous waste.
Although glycine has been shown to neutralize glutaraldehyde (see H. Y. Cheung and M. R. W. Brown, Evaluation of Glycine As An Inactivator of Glutaraldehyde, ASP-934 J. Pharm. 211 (1982)), the toxicity of reaction products of glycine has not been studied. Therefore, it is not known from this article whether the reaction product is nonhazardous. Accordingly, it is desirable to have a neutralizer that effectively neutralizes aldehydes in compliance with environmental standards and is less toxic to the environment.
Furthermore, it has been observed that neutralization of aldehydes with amino acids under acidic conditions may reversibly form compounds called Schiff""s bases. That is, once the Schiff""s bases are formed under acidic conditions, the reverse reaction will occur to release back aldehydes. Another problem associated with amino acid neutralized aldehydes is that often the solution formed between the aldehyde and the amino acid has a dark color such as dark green or black. This occurs, for example, during the neutralization reaction between o-phthalaldehyde and the amino acid, glycine. Such color appearance has the perception that the resulting solution is not environmentally friendly even though the solution has been neutralized. Finally, not all methods relating to formation of neutralized aldehydes are as environmentally friendly as others are. This invention is intended to overcome the foregoing shortcomings relating to neutralization of aldehydes as hereinafter described.
Methods, compositions and devices are disclosed for neutralizing aldehydes to form a nonhazardous product which is non-reversible and environmentally friendly. In one aspect, the invention provides a generally nonhazardous means for neutralizing and reducing aldehydes to form environmentally friendly amino acids.
In one embodiment, the neutralization method comprises combining an amino acid in solution or in solid form with an aldehyde to form a neutralized aldehyde and then reducing the neutralized aldehyde to form an amino acid. Devices for neutralizing and reducing the aldehyde to an amino acid are also disclosed.
Among the advantages of the invention are: a more environmentally friendly end product as the reduced neutralized aldehydes are amino acids and are very similar in backbone structure to natural amino acids, and thus would be expected to be biodegradable and environmentally friendly; the prevention of possible reformation of the aldehydes from the Schiff""s bases since the reduction of a Schiff""s base is irreversible; the colors of the reduced neutralized aldehydes are pale, not dark or black which would reflect the appearance of a non-toxic material; and once reduced, there would be no further need to treat the waste and the waste could be immediately discharged.
Additional features, embodiments, and benefits will be evident in view of the figures and detailed description presented below.